Problems with inside the wall dryer vent

We have an quirky old condo (1965) with the dryer vent running up inside the wall, then through the ceiling over the shower to the outside. The builders did this because a shower stall is between the washer/dryer closet and the outside.
The previous owners were running the dryer vent inside through some kind of filter box. The outside of the vent is stopped up with some kind of sealant.
Do you think one of those professional vent cleaning companies can open this vent pipe up so we can run our dryer? Or is that pipe not safe and should we rip out the walls and replace it?
Also how could the previous owners have possibly run that vent inside the house? The vent goes to this little box on the wall, maybe it filters the lint. But the moisture?

Problems with inside the wall dryer vent

I don't see a problem with using a quailfied vent cleaning co on your exsiting setup.. that's their trade. you'd want someone who specializes in dryers. Assuming the original vent is rigid pipe and they can remove the sealer closing off the outlet. they prob' did that cause vent kept blocking up. what are your neighbors doing? might have to have it cleaned on a regular basis..hope this is an electric dryer[gas would be dangerous=c0]..in any event; yeah that's not healthy-having that moisture in room.